1. Field of the Invention
The present invention relates to a hub for measuring the torque of a cycle wheel, as well as a cycle wheel equipped with such a torque-measuring hub. The invention also relates to a hub for measuring the power of a cycle wheel, as well as a cycle wheel equipped with such a hub.
2. Background Information
Measuring the driving power of a cycle wheel is of interest in a number of cases, for example in evaluating the performance of a cyclist during training. The power generated by the cyclist can be determined by multiplying the cycle speed by the driving force transmitted by the cyclist to the drive wheel. However, measuring this force is relatively complex, and in the context of the present invention, the power is determined by multiplying the engine torque, transmitted by the cyclist to the drive wheel, by the angular velocity of the wheel.
U.S. Pat. No. 6,418,797 discloses a two-part hub for measuring the power of a cycle wheel. A driving part of the hub, rotationally movable about a fixed axis of the wheel, is rotationally driven by the cyclist who pedals, by means of a freewheel device. A driven part of the hub, within which the driving part is housed, is radially separated from the driving part by ball bearings. A connecting element, which supports strain gauges, is fixed to both the driving part and the driven part of the hub. Thus, when in use, the connecting element transmits the engine torque generated by the cyclist to the driven part, and the connecting element strains. The strain of the connecting element is measured by the strain gauge and makes it possible to obtain a measurement of the engine torque generated by the cyclist. Furthermore, a sensor measures the angular velocity of the drive wheel, which makes it possible to obtain a measurement of the power developed by the cyclist, by multiplying the engine torque by the angular velocity. Such a device is heavy and cumbersome, because it requires the presence of a relatively massive connecting element to support the strain gauges. Furthermore, the various gauges are glued to various locations of the connecting element; and they must be connected to one another by wires that are also glued to the connecting element. The fixing of separate components to the connecting element poses problems that affect manufacturing quality and reliability of the electronics.